This invention relates to a new, improved and precise rotary displacement measuring apparatus in which absolute measurement of rotary position may be made.
In the operation of various mechanical and electromechanical systems, it is necessary to monitor the position and displacement of either some element of the system or some object which is not part of the system. For example, in robotic systems it is almost always necessary to monitor and control the movement and position of various component parts of the systems, such as an arm, fingers or other grasping elements, etc. Such monitoring and control yields the dexterity and precision required for a robotic system to carry out its functions.
Two types of position and displacement measurement may be required in the above-described systems, these being linear displacement and position and angular or rotary displacement and position. Prior art mechanisms for sensing rotary position and displacement most often utilized a direct connection between the article or object whose position or displacement was to be monitored, and some type of gauge, needle or other visual indicator. Of course, such mechanisms were typically large, cumbersome, unreliable, and lacked precision in carrying out the monitoring function.
A number of electrical and electronic devices have been proposed for measuring angular position and displacement including so-called rotary variable differential transformers, such as described in U.S. Pat. No. 4,910,488. These devices provide for measuring angular displacement by converting mechanical rotation into an analog electrical signal. Electronic rotary position and displacement measuring apparatus has also been proposed as disclosed in co-pending U.S. application Ser. No. 07/478,266, filed Feb. 12, 1990. The above-mentioned electrical and electronic measuring devices, although reducing the bulkiness and imprecision problems of the prior art mechanisms, such devices still do not allow for the precision oftentimes desired in the mechanical and electromechanical systems in use or contemplated for use at the present time.
Other types of rotary displacement and position measuring transducers include resistance-based voltage dividers and optical encoders, both of which also suffer from one or more of the disadvantages mentioned above.